diff --git a/src/platform/types/theme.ts b/src/platform/types/theme.ts
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+++ b/src/platform/types/theme.ts
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+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export type ThemeManifest = Partial<{
+    /**
+     * Version number of the theme manifest.
+     * This must be incremented when backwards incompatible changes are introduced.
+     */
+    version: number;
+    // A user-facing string that is the name for this theme-collection.
+    name: string;
+    /**
+     * This is added to the manifest during the build process and includes data
+     * that is needed to load themes at runtime.
+     */
+    source: {
+        /**
+         * This is a mapping from theme-id to location of css file relative to the location of the
+         * manifest.
+         * eg: {"element-light": "theme-element-light.10f9bb22.css", ...}
+         *
+         * Here theme-id is 'theme-variant' where 'theme' is the key used to specify the manifest
+         * location for this theme-collection in vite.config.js (where the themeBuilder plugin is
+         * initialized) and 'variant' is the key used to specify the variant details in the values
+         * section below.
+         */
+        "built-asset": Record<string, string>;
+        // Location of css file that will be used for themes derived from this theme.
+        "runtime-asset": string;
+        // Array of derived-variables
+        "derived-variables": Array<string>;
+    };
+    values: {
+        /**
+         * Mapping from variant key to details pertaining to this theme-variant.
+         * This variant key is used for forming theme-id as mentioned above.
+         */
+        variants: Record<string, Variant>;
+    };
+}>;
+
+type Variant = Partial<{
+    /**
+     * If true, this variant is used a default dark/light variant and will be the selected theme
+     * when "Match system theme" is selected for this theme collection in settings.
+     */
+    default: boolean;
+    // A user-facing string that is the name for this variant.
+    name: string;
+    /**
+     * Mapping from css variable to its value.
+     * eg: {"background-color-primary": "#21262b", ...} 
+     */
+    variables: Record<string, string>;
+}>;